518 POLYPI. 



FAMILY III. 

 CORTICATL 



This family comprises genera in which all the Polypi are con- 

 nected by a common, thick, fleshy or gelatinous substance, in the 

 cavities of which they are received, and which envelopes an axis 

 varying in form and substance. The Polypi of those that have been 

 observed are somewhat more complex than the preceding ones and 

 approximate more closely to the Actinae, Internally we observe a 

 stomach from which eight intestines originate, two that are pro- 

 longed into the common mass, and two that are shorter,,and seem 

 to supply the place of ovaries. 



They are subdivided into four tribes. In the first, or the Ceea- 

 TOPHYTA, the internal axis has the appearance of wood or horn, 

 and is fixed. Two genera of them are known, and both extremely 

 numerous. 



Antipathes, Lin. 



Commonly termed Black Coral, where the ramous and ligneous-like sub- 

 stance of the axis is enveloped v/ith a bark so soft, that it becomes destroy- 

 ed after death, when it resembles branches of dry wood, &c. 



GOEGONIA, L. 

 Where, on the contrary, this horny or ligneous substance of the axis is 

 enveloped by a bark, the thickness of which is so penetrated by calcareous 

 granules, that it dries on the axis, retaining its colours, wliich arc frequently 

 extremely vivid and beautiful; it is soluble in acids. 



In the second tribe, that of the Litiiophyta, the internal axis 

 is of a strong substance and fixed. In 



Isis, Lin. 

 This axis is ramous, and has no cells or cavities on its surface . The ani- 

 mal bai-k which envelopes it is mixed with calcareous granules, as in the 

 Gorgoniae. 



Madrepoea, Lin. 

 The stony portion of Madrepores is either ramous, or forms rounded mosses, 

 or leaves, but is always furnished with lamellje vvrhich unite concentrically in 

 points where they represent stars, or which terminate in lines more or less 

 serpentine. While alive, this stony portion is covered with a living bark. 



